(We should remember that a 90's hand-count of actual attendance at American churches on a given Sunday showed that the numbers present were much lower than the number of Americans who told surveyors they attended Church every Sunday. 48% said they attended every Sunday but only 25% were actually in the pews when the count took place. There is a natural, built-in inflation factor here since people are often answering based upon the fact that they mean to be there every Sunday or think of themselves as a regular church-goer. The actual numbers in the pew on a given Sunday are almost certainly considerably lower than self-reporting would indicated.)

Twice as many Catholics - 56% - report that they are never or rarely attend or only attend a few times a year.

21% attend at least once a month (which in some US dioceses and in Australia is the standard to be considered a "practicing" Catholic.)

So using this as a standard, that would mean about 44% of US Catholics would be considered "practicing" and 56% "non-practicing."

Which looks fairly dismal until you compare it to other western countries like Australia where only 15% of Catholics attend Mass once a month. In France, weekly attendance is usually put at less than 5%, under 10% in deeply Catholic Austria, etc. so you can see why the Pope might look with respect and interest on a western country that is still overtly religious in its public life and possesses a huge and relatively vibrant Catholic population.